1. Field of the Invention
The present invention provides an aluminosilicate ceramic product, such as a proppant for gas and oil well fracturing and a method of forming the product. The proppant is used in a conventional manner to maintain a fracture in a subterrainian formation in a propped condition.
2. Description of the Prior Art
Hydraulic fracturing is a well stimulation technique designed to increase the productivity of a well by creating highly conductive fractures or channels in the producing formation surrounding the well. The process normally involves injecting a fluid at a sufficient rate and pressure to rupture the formation thereby creating a crack or fracture in the rock, and thereafter placing a particulate material or propping agent in the formation to maintain the fracture walls open by resisting forces tending to close the fracture. The propping agent or proppant must have sufficient mechanical strength to bear the closure stresses, provide relatively high permeability in the propped fracture, and resist chemical attack by liquids or gasses in the formation.
The literature describes numerous materials that apparently would be suitable for use as proppants. For instance, U.S. Pat. No. 3,497,008, entitled "Method of Propping Fractures with Ceramic Particles", describes proppant particles having a preferred composition of hard glass. Typical glass compositions identified in the patent include soda-lime-silica, aluminosilicate, borosilicate, soda-zinc-silica, soda-barium-silica, high silica, and aluminoborosilicate. The patent also identifies other ceramic materials and porcelains usable as proppants, such sintered alumina, steatite, and mullite.
Additional examples of proppants are described in U.S. Pat. No. 3,976,138, entitled "Method of Increasing Permeability in Subsurface Earth Formation". Table 1 of this reference illustrates four samples of alumina pellets that are supposedly suitable for use as proppants.
Other materials are described in U.S. Pat. No. 3,998,271, entitled "Multiple Fracturing of Subterrainian Formations"; U.S. Pat. No. 4,029,148, entitled "Well Fracturing Method"; and U.S. Pat. No. 4,068,718, entitled "Hydraulic Fracturing Method Using Sintered Bauxite Propping Agent".
Also known are various techniques for forming pellets from bauxitic clays. For instance, U.K. Patent Application No. 2,037,727, entitled "Sintered Spherical Ceramic Pellets for Gas and Oil Well Proppants", describes a process for manufacturing spherical sintered ceramic pellets of bauxite. U.S. Pat. No. 3,888,311, entitled "Hydraulic Fracturing Method", describes a method of preparing cement pellets. U.S. Pat. No. 4,251,265, entitled "Clay Preparation", describes a process for pelletizing as-mined clay that includes the steps of crushing the clay to within an appropriate size range, blending the crushed clay with water to achieve a desired moisture content, pelletizing the clay in a suitable apparatus to provide clay pellets of predetermined size, surface hardening the pellets, and drying and calcining the pellets at an elevated temperature.